Photoactivation of hyaluronidase by chlorpromazine

The effects of UVA and chlorpromazine on the activity of hyaluronidase were investigated. Hyaluronidase was slightly activated by UVA alone. It was also activated by chlorpromazine, but the activation was enhanced by concomitant UVA irradiation. By pre-irradiation of chlorpromazine, it was found that a stable photoproduct of chlorpromazine was formed that activated hyaluronidase. As activation of hyaluronidase has been described in relation to tissue inflammation, the onset of chlorpromazine-induced photosensitivity may, in part, be related to the hyaluronidase activating effect of chlorpromazine plus UVA.